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5-Hydroxyindoleacetic Acid (Urine)

Does this test have other names?

5-Hydroxyindoleacetic acid urine, 5-HIAA, HIAA

What is this test?

This test finds out how much 5-hydroxyindoleacetic acid (5-HIAA) is in your urine.

Your liver breaks down the hormone serotonin into 5-HIAA. This waste product is normally sent from your body in your urine. Tumors called functioning carcinoids secrete serotonin. Carcinoid tumors are found in the intestinal tract, lungs, appendix, and other body tissues. Because serotonin in the blood is broken down very quickly, the amount of 5-hydroxyindoleacetic acid collected in the urine over a full day more accurately reflects the rate at which serotonin is being made than the blood level at one particular time.

Why do I need this test?

You may need this test if you have symptoms of a carcinoid tumor. Carcinoid tumors can occur anywhere, but most start in the small bowel. Signs and symptoms include:

Flushing in your face and neck

Diarrhea and abdominal cramps

Nausea and vomiting

Low blood pressure

Unexplained weight loss

Irregular heartbeat

Watery eyes

Asthma-like respiratory symptoms

Sexual dysfunction in men

What other tests might I have along with this test?

Your healthcare provider may also order a biopsy to help diagnose a tumor. A tumor marker protein, chromogranin A, may be ordered as a blood test. Your provider may also order a liver scan if he or she suspects that the tumors have spread.

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

Normal results are 3 to 15 milligrams (mg) of 5-HIAA over 24 hours. Women generally have lower levels than men.

Higher levels of 5-HIAA may mean you have:

Carcinoid tumors

Noncarcinoid tumors

Cystic fibrosis

Malabsorption

Lower levels of 5-HIAA may mean you have:

Depression

Migraines

How is this test done?

This test needs a 24-hour urine sample. For this sample, you must collect all of your urine for 24 hours. Empty your bladder completely first in the morning without collecting it. Note the time. Then collect your urine every time you go to the bathroom over the next 24 hours.

How do I get ready for this test?

Don't eat foods containing serotonin for at least 3 days before the test or during the testing period. You may also need to stop taking certain medicines before the test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.

If you are doing a 24-hour test, make sure you understand how to collect the sample. Ask if there are any foods you should not eat before or during the test.